The present invention relates to brake actuators, and more particularly to a brake actuator of the hand-operated type in which a hand grip is rotated to release a pawl for enabling brake releasing movement of a brake lever.
A parking brake actuating assembly is typically installed in a passenger compartment of a motor vehicle adjacent the driver""s seat. The motor vehicle has a brake system that is actuated to prevent vehicle wheel rotation and hence rolling movement of the vehicle by applying tension to a vehicle brake cable that connects to the brake system.
The typical parking brake actuating assembly comprises a stationary sector having a plurality of teeth. A brake lever is mounted for pivotal movement relative to the sector and is adapted to be operatively connected to the vehicle brake cable. The brake lever is pivotable in a brake applying direction to apply tension to the vehicle brake cable and in a brake releasing direction opposite the brake applying direction to release tension on the brake cable and release the vehicle brakes. A pawl is normally mounted to the brake lever for movement between engaged and disengaged positions relative to the sector teeth. When the pawl is in the engaged position and the brake lever is in the braking position, the pawl engages the teeth to prevent the brake lever from pivoting in the brake releasing direction. When pawl is in the disengaged position, the pawl disengages from the teeth to allow the brake lever to pivot from the braking position thereof towards and into the released position thereof. An elongated release member is mounted to the brake lever for longitudinal movement relative to the brake lever between normal and depressed positions. An activation button, which protrudes out of an outer end of the brake lever, is connected to an outer end of the release member. An inner end of the release member is connected to the pawl such that when the release member is moved into the depressed position, the pawl is forced into the disengaged position.
In this type of brake actuator assembly, the tension created in the brake cable system when the lever is in the brake applied position tends to force the pawl into a binding engagement with the sector teeth. To move the lever to its brake released position, the user must first lift the brake lever in the brake applying direction to remove the cable tension load from the pawl and then depresses the activation button to disengage the pawl. This is because the button is typically depressed with the user""s thumb, which typically does not have enough strength to overcome the binding engagement between the pawl and the sector. Additionally, to move the lever further in the brake applying direction prior to depressing the button, the user must apply more force to the lever than was originally used to apply the brake. This can be a problem, for example, where a strong person applies the brake and then later a weaker person attempts to release the brake. It would be desirable to provide a system whereby the use of this push-button and the additional step of lifting the lever prior to releasing the brakes are eliminated.
U.S. Pat. No. 2,248,364 discloses a twist release type hand brake actuator that eliminates the use of a push button. In the ""364 patent, the user rotates a hand grip on the end of the lever to disengage the pawl from the sector with which it is engaged. The hand grip has a cam structure mounted internally thereof that engages a pin. This pin is fixed on a rod that is connected to a plate that has a lug thereon. Rotation of the hand grip cams the cam structure against the pin so that the pin is forced outwardly with respect to the lever to pull the rod, which in turn pulls the plate. The plate has a lug thereon the engages the pawl to pivot it out of engagement with the sector. A spring is connected between the pawl and the plate. When the pawl is disengaged by the lug, the spring functions to bias the rod and plate back to their normal positions whereat the lug will disengage from the pawl; and upon disengagement of the lug from the pawl, the spring functions to pivot the pawl into engagement with the sector.
The construction disclosed in the ""364 patent has certain shortcomings. For example, the cam and pin mechanism that translates rotation of the hand grip into movement of the rod is mounted internally to the hand grip. This is undesirable because it increases the complexity of the grip itself, which must include suitable internal components for providing the translating action. Further, the plate and spring arrangement used to disengage and bias the pawl are relative complex and difficult to assemble, which leads to increased part and manufacturing complexity and cost.
One aspect of the invention provides with an improved location for its translation mechanism for translating rotational movement of the hand grip to substantially linear movement of a link for releasing the pawl. The actuator comprises a mounting bracket constructed to mount the brake actuator in a passenger compartment of the motor vehicle; a sector provided on the mounting bracket and having a plurality of teeth; and a brake lever mounted for movement relative to the mounting bracket and the sector. The brake lever includes a linkage connector constructed to be connected to the brake actuating linkage. The brake lever is movable in a brake applying direction to actuate the brake actuating linkage and in a brake releasing direction opposite the brake applying direction to release the brake actuating linkage. A pawl is mounted to the brake lever for movement between engaged and disengaged positions relative to the teeth of the sector. The pawl engages the teeth of the sector to prevent the brake lever from pivoting in the brake releasing direction when in the engaged position, and in the disengaged position is disengaged from the teeth to allow the brake lever to pivot in the brake releasing direction.
A pawl release system comprises a rotatable hand grip rotatably mounted on a free end of the lever and an elongated link extending inwardly along the lever. The link may be comprised by one or more components, but may be a singular rod. The link is connected to the pawl and movable in a shifting manner such that movement of the link in a pawl releasing direction moves the pawl from the engaged position thereof to the disengaged position thereof, thus enabling the brake lever to be moved in the brake releasing direction thereof. The link may be curved or comprised of components joined at an angle, and the shifting movement is any type of movement, such as a linear movement, that effects movement of the pawl. A translation mechanism is mounted on the lever proximally of the hand grip and couples the hand grip to the link such that rotation of the hand grip is translated to affect movement of the link in the pawl releasing direction to move the pawl from the engaged position thereof to the disengaged position thereof. At least one spring is constructed to bias the pawl release system to normally maintain the pawl in the pawl engaged position thereof. The spring may bias the pawl directly, or may bias it indirectly via the link and/or the hand grip.
On advantage of having the translation mechanism mounted on the lever inward of the hand grip, as opposed to inside the hand grip, is that the hand grip can be made smaller, saving valuable space in the passenger compartment.
Another aspect of the invention provides an improved arrangement for providing a hand-operated brake actuator for actuating a brake actuating linkage connected to a brake system of a motor vehicle. The actuator comprises a mounting bracket constructed to mount the brake actuator in a passenger compartment of the motor vehicle; a sector provided on the mounting bracket and having a plurality of teeth; and a brake lever mounted for movement relative to the mounting bracket and the sector. The brake lever includes a linkage connector constructed to be connected to the brake actuating linkage. The brake lever is movable in a brake applying direction to actuate the brake actuating linkage and in a brake releasing direction opposite the brake applying direction. A pawl is mounted to the brake lever for movement between engaged and disengaged positions relative to the teeth of the sector. The pawl engages the teeth of the sector to prevent the brake lever from pivoting in the brake releasing direction when in the engaged position; and in the disengaged position is disengaged from the teeth to allow the brake lever to pivot in the brake releasing direction.
A pawl release system comprises a rotatable hand grip rotatably mounted on a free end of the lever. A rigid rod extends inwardly along the lever. The rod may be curved, straight, or may be constituted by smaller rods or other substantially rigid members coupled together. The rod is connected to the pawl and movable in a substantially linear manner such that movement of the rod inwardly relative to the lever in a pawl releasing direction moves the pawl from the engaged position thereof to the disengaged position thereof, thus enabling the brake lever to be moved in the brake releasing direction thereof. A translation mechanism is mounted proximally of the hand grip and couples the hand grip to the rod such that rotation of the hand grip is translated to affect inward movement of the rod in the pawl releasing direction to move the pawl from the engaged position thereof to the disengaged position thereof. The system also includes a pair of spring seats. One of the spring seats is a fixed spring seat, which may be provided by the lever, by one of the other components of the pawl release system, or by any other suitable structure. The other spring seat is provided on the rod. At least one spring is constructed to bias the pawl release system to normally maintain the pawl in the pawl engaged position thereof. The at least one spring includes a rod biasing spring positioned between the spring seats so as to bias the rod in a pawl engaging direction opposite the pawl releasing direction.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.